Our bubble did a trick like that at night (in fact it looked just marginally better than that one with the skeleton showing in only one spot). It had been through a lot getting to our tank so I expected some problems, but it'd only do that at night which was weird. Turns out that at night when it tried to extend its feeder tentacles, the flow was too much for it. Adjusted the flow a litle and moved the coral and now it is fine.
The first time I saw it, I immediately killed the flow, and squirted cyclopeeze at it in hopes of getting it to eat (I only get to see the tank every other weekend at best due to this funny thing called college and work that people keep telling me about and I wanted to make sure it was in good health before I left again).
Good luck.